The present invention refers to a roller or belt correction device for lateral alignment, during converting, of partly folded sheet-like or plate-like workpieces in a folder-gluer, which is a machine, that is commonly used in the packaging industry, for example, for manufacturing carton boxes from cut plate-like workpieces.
Working continually with moving workpieces, often in this kind of machine the folding and gluing operations are preceded by a lateral aligning operation of the travelling workpieces, this in order to avoid considerable complications at the level of the converting elements.
Such machines, which comprise a succession of modules, the number of which depend on the complexity of the manufacturing operations required by the type of box chosen, generally consist of at least a feeder feeding the box production blank by blank from a pile, a breaker prebreaking the first and third creases to 180.degree. then reopening the blank, a module of folders with hooks, which fold the front flaps then the rear flaps of the blank to 180.degree., a gluing station, a helical guide and conical roller for folding the second and fourth creases of the blank, a pressing device, which compresses the second and fourth creases and arranges the boxes in a stream and, finally, a delivery module, which receives the boxes while keeping them pressed to allow the glue to dry.
The blanks are conveyed from one station to the other by means of belt conveyors, which frictionally seize the blank either between lower and upper belts or between lower belts and upper support rollers. Such lower and upper conveying devices are often associated with means for orientating the workpieces in a determined position at the inlet of the production line. In the case of folder-gluers, it is in fact necessary that each blank is accurately aligned with one lateral side parallel to the conveying direction before doing any folding operation. If this lateral alignment achieves at the inlet of the machine, generally by the feeder introducing the blanks one by one on the belt conveyors in a position being already accurately laterally aligned, no aligning device will be provided along the conveying path of the blank in the modules or stations downstream the feeder, where the travelling workpieces have already been partly converted by the folder-gluer. This is due to the fact that in a production process such as previously described, once the blank being well aligned, it can be converted into a box without the folding or gluing operations interfering with its lateral alignment.
However, some folding operations require even for the manufacturing of a very simple box a quite complex mechanism, which is expensive and sophisticated due to the production expectations imposing still higher rates with a most perfect quality. In the traveling direction of the blanks, even if a front flap can be folded without difficulty by a simple hook pivoting around a pull-back spring, the folding of the rear flaps will be a problem. In fact, the rear flaps have to be turned in their traveling direction and require a rotary folder being electronically controlled by drive motors, which constantly have to catch up in their movement with the flap since the latter tends to flee due to its traveling, while ensuring a progressive and soft folding by a path being modulated and adapted to the size of the flaps. The sheet-like or plate-like blanks having low specific gravity render such an operation and the adjustments more or even too delicate for a profitable and competitive industrial use. The application of such rotary folders on every folder-gluer irreducibly involves a considerable and undesired increase in price of the necessary equipment for the realization of a large number of jobs. This drawback mainly results from the above-mentioned manufacturing method of these boxes.
Another main drawback of such a method arises from the creation of particular boxes being made from complicated blanks, which require, to complete their transformation, more than one passage through a folder-gluer before obtaining the desired completed product.
To meet these difficulties, Swiss patent application No 1997 1274/97 proposes a belt conveying device modifying the manufacturing method by pivoting, in the horizontal plane, the travelling workpieces of low specific gravity one by one. In this invention, once the front flaps of the blank have been folded by the front hooks, it is sufficient to repeat the same operation for the rear flaps after having pivoted the blank on itself of a half-turn in the horizontal plane. This alternative complies with a double criterion aimed to improve the production, on the one hand, by reducing to half the number of passages necessary for certain boxes having a complicated folding, and, on the other hand, by reducing as much as possible the manufacturing costs of such machines.
While the pivoting of boxes avoids the expensive use of a rotary folder and reduces the number of passages in machine for the manufacture of certain types of boxes, a drawback exists of breaking off the constancy of the initial lateral alignment of the workpiece traveling in the folder-gluer.